A decline in dehydroepiandrosterone (DHEA) and growth hormone (GH) levels with aging may be associated with frailty and morbidity. Little is known about the direct effects of DHEA on somatotropes. We recently reported that 17-estradiol (E2), a DHEA metabolite, stimulates expression of GH in vitro in young female rats. To test the hypothesis that DHEA restores function in aging somatotropes, dispersed anterior pituitary (AP) cells from middle aged (12-14 months) or young (3-4 months) female rats were cultured in vitro +/- DHEA or E2 and fixed for immunolabeling or in situ hybridization. E2 increased percentages of AP cells with GH protein or mRNA in the aged rats to young levels. DHEA increased percentages of somatotropes (detected by GH protein or mRNA) from 14-16%±2 to 29-31%±3 (P 0.05) and GH mRNA (detected by QRT-PCR), only in aging rats. To test DHEA's in vivo effects, 18-month old female rats were injected with DHEA or vehicle for 2.5 days, followed by a bolus of GH releasing hormone (GHRH), 1 h before sacrifice. DHEA treatment increased serum GH 1.8 fold [7 ± 0.5 to 12 ± 1.3 ng/ml (P = 0.02, RIA)] along with a similar increase (P = 0.02) in GH immunolabel. GHRH target cells also increased from 11%±1 to 19%±2 (P = 0.03). Neither GH nor GHRH receptor (GHRH R) mRNAs levels were changed. To test mechanisms behind DHEA's actions, AP cells from aging rats were treated with DHEA +/- inhibitors of DHEA metabolism. Trilostane, aminogluthemide or ICI 182,780, completely blocked the stimulatory effects of DHEA, suggesting that DHEA metabolites may stimulate aging somatotropes via estrogen receptors.